The AAS Flow Rate System has two options available to the end user for the detection and/or measurement of water flow thru your Automated Aquarium System. One option is the use of a simple Flow Switch (AAS FL-135815) that provides a Flow/No Flow indication signal back to the AAS CPU Controller for alarming and/or pump shutdown. The second and more sophisticated option, is a Flow Rate Sensor (AAS FL-E33110-30 ) that provides not only flow/no flow status but at what flow rate in GPM your system pump is circulating the Aquarium water thru your tank. This second option can provide data that warns the user of a potential flow related problem prior to a complete shutdown so that preventative maintenance can be performed. The Flow Rate Sensor is made of Polypropylene and is able to resist temperatures up to 160F (71C). Both the Flow Switch and Flow Rate Sensor are mounted in a Tee-Fitting in the Return Line of your filter system directly at the output of your pump. The Flow Rate Sensor outputs a pulse train that is sent to the AAS CPU Controller for processing where it is then displayed on the AAS User Interface in units of GPH. Also as stated earlier, the ASS CPU Controller can shut-down the Pump if a "No-Flow" condition exist to protect the pump from running dry.